Connective tissue is a required component of all mammals. It provides rigidity, differentiation, attachments, and, in some cases, elasticity. Connective tissue components include, for example, collagen, elastin, proteoglycans, fibronectin, and laminin. These biochemicals make up (or are components of) structures, such as skin, bone, teeth, tendon, cartilage, basement membrane, blood vessels, cornea, and vitreous humor.
Under normal conditions, connective tissue turnover and/or repair processes are in equilibrium with connective tissue production. Degradation of connective tissue is carried out by the action of proteinases released from resident tissue cells and/or invading inflammatory or tumor cells.
Matrix metalloproteinases, a family of zinc-dependent proteinases, make up a major class of enzymes involved in degrading connective tissue. Matrix metalloproteinases are divided into classes, with some members having several different names in common use. Examples are: MMP-1 (also known as collagenase 1, fibroblast collagenase, or EC 3.4.24.3); MMP-2 (also known as gelatinase A, 72 kDa gelatinase, basement membrane collagenase, or EC 3.4.24.24), MMP-3 (also known as stromelysin 1 or EC 3.4.24.17), proteoglycanase, MMP-7 (also known as matrilysin), MMP-8 (also known as collagenase II, neutrophil collagenase, or EC 3.4.24.34), MMP-9 (also known as gelatinase B, 92 kDa gelatinase, or EC 3.4.24.35), MMP-10 (also known as stromelysin 2 or EC 3.4.24.22), MMP-11 (also known as stromelysin 3), MMP-12 (also known as metalloelastase, human macrophage elastase or HME), MMP-13 (also known as collagenase 111), and MMP-14 (also known as MT1-MMP or membrane MMP). See, generally, Woessner, J. F., “The Matrix Metalloprotease Family” in Matrix Metalloproteinases, pp. 1–14 (Edited by Parks, W. C. & Mecham, R. P., Academic Press, San Diego, Calif. 1998).
Excessive breakdown of connective tissue by MMPs is a feature of many pathological conditions. Inhibition of MMPs therefore provides a control mechanism for tissue decomposition to treat these pathological conditions. Such pathological conditions generally include, for example, tissue destruction, fibrotic diseases, pathological matrix weakening, defective injury repair, cardiovascular diseases, pulmonary diseases, kidney diseases, liver diseases, and diseases of the central nervous system. Specific examples of such conditions include, for example, rheumatoid arthritis, osteoarthritis, septic arthritis, multiple sclerosis, a decubitis ulcer, corneal ulceration, epidermal ulceration, gastric ulceration, tumor metastasis, tumor invasion, tumor angiogenesis, periodontal disease, liver cirrhosis, fibrotic lung disease, emphysema, otosclerosis, atherosclerosis, proteinuria, coronary thrombosis, dilated cardiomyopathy, congestive heart failure, aortic aneurysm, epidermolysis bullosa, bone disease, Alzheimer's disease, defective injury repair (e.g., weak repairs, adhesions such as post-surgical adhesions, and scarring), chronic obstructive pulmonary disease, and post myocardial infarction. MMPs (particularly MMP-9) also have been reported to be associated with pathological conditions related to nitrosative and oxidative stress. See Gu, Zezong et al., “S-Nitrosylation of Matrix Metalloproteinases: Signaling Pathway to Neuronal Cell Death,” Science, vol. 297, pp. 1186–90 (2002).
Matrix metalloproteinases also are involved in the biosynthesis of tumor necrosis factors (TNFs). Tumor necrosis factors are implicated in many pathological conditions. TNF-α, for example, is a cytokine that is presently thought to be produced initially as a 28 kD cell-associated molecule. It is released as an active, 17 kD form that can mediate a large number of deleterious effects in vitro and in vivo. TNF-α can cause and/or contribute to the effects of inflammation (e.g., rheumatoid arthritis), autoimmune disease, graft rejection, multiple sclerosis, fibrotic diseases, cancer, infectious diseases (e.g., malaria, mycobacterial infection, meningitis, etc.), fever, psoriasis, cardiovascular diseases (e.g., post-ischemic reperfusion injury and congestive heart failure), pulmonary diseases (e.g., hyperoxic alveolar injury), hemorrhage, coagulation, radiation damage, and acute phase responses like those seen with infections and sepsis and during shock (e.g., septic shock and hemodynamic shock). Chronic release of active TNF-α can cause cachexia and anorexia. TNF-α also can be lethal.
Inhibiting TNF (and related compounds) production and action is an important clinical disease treatment. Matrix metalloproteinase inhibition is one mechanism that can be used. MMP (e.g., collagenase, stromelysin, and gelatinase) inhibitors, for example, have been reported to inhibit TNF-α release. See, e.g., Gearing et al., Nature, 370, 555–557 (1994). See also, McGeehan et al., Nature, 370, 558–561 (1994). MMP inhibitors also have been reported to inhibit TNF-α convertase, a metalloproteinase involved in forming active TNF-α. See, e.g., WIPO Int'l Pub. No. WO 94/24140. See also, WIPO Int'l Pub. No. WO 94/02466. See also, WIPO Int'l Pub. No. WO 97/20824.
Matrix metalloproteinases also are involved in other biochemical processes in mammals. These include control of ovulation, post-partum uterine involution, possibly implantation, cleavage of APP (β-amyloid precursor protein) to the ainyloid plaque, and inactivation of (α1-protease inhibitor (α1-PI). Inhibiting MMPs therefore may be a mechanism that may be used to control of fertility. In addition, increasing and maintaining the levels of an endogenous or administered serine protease inhibitor (e.g., α1-PI) supports the treatment of pathological conditions such as emphysema, pulmonary diseases, inflammatory diseases, and diseases of aging (e.g., loss of skin or organ stretch and resiliency).
Numerous metalloproteinase inhibitors are known. See, generally, Brown, P. D., “Synthetic Inhibitors of Matrix Metalloproteinases,” in Matrix Metalloproteinases, pp. 243–61 (Edited by Parks, W. C. & Mecham, R. P., Academic Press, San Diego, Calif. 1998).
Metalloproteinase inhibitors include, for example, natural biochemicals, such as tissue inhibitor of metalloproteinase (TIMP), α2-macroglobulin, and their analogs and derivatives. These are high-molecular-weight protein molecules that form inactive complexes with metalloproteinases.
A number of smaller peptide-like compounds also have been reported to inhibit metalloproteinases. Mercaptoamide peptidyl derivatives, for example, have been reported to inhibit angiotensin converting enzyme (also known as ACE) in vitro and in vivo. ACE aids in the production of angiotensin II, a potent pressor substance in mammals. Inhibiting ACE leads to lowering of blood pressure.
A wide variety of thiol compounds have been reported to inhibit MMPs. See, e.g., WO95/13289. See also, WO96/11209. See also, U.S. Pat. No. 4,595,700. See also, U.S. Pat. No. 6,013,649.
A wide variety of hydroxamic acid compounds also have been reported to inhibit MMPs. Such compounds reportedly include hydroxamic acids having a carbon backbone. See, e.g., WIPO Int'l Pub. No. WO 95/29892. See also, WIPO Int'l Pub. No. WO 97/24117. See also, WIPO Int'l Pub. No. WO 97/49679. See also, European Patent No. EP 0 780 386. Such compounds also reportedly include hydroxamic acids having peptidyl backbones or peptidomimetic backbones. See, e.g., WIPO Int'l Pub. No. WO 90/05719. See also, WIPO Int'l Pub. No. WO 93/20047. See also, WIPO Int'l Pub. No. WO 95/09841. See also, WIPO Int'l Pub. No. WO 96/06074. See also, Schwartz et al., Progr. Med. Chem., 29:271–334(1992). See also, Rasmussen et al., Pharmacol. Ther., 75(1): 69–75 (1997). See also, Denis et al., Invest New Drugs, 15: 175–185 (1997). Various piperazinylsulfonylmethyl hydroxamic acids and piperidinylsulfonylmethyl hydroxamic acids have additionally been reported to inhibit MMPs. See, WIPO Int'l Pub. No. WO 00/46221. And various aromatic sulfone hydroxamic acids have been reported to inhibit MMPs. See, WIPO Int'l Pub. No. WO 99/25687. See also, WIPO Int'l Pub. No. WO 00/50396. See also, WIPO Int'l Pub. No. WO 00/69821.
It is often advantageous for an MMP inhibitor drug to target a certain MMP(s) over another MMP(s). For example, it is typically preferred to inhibit MMP-2, MMP-3, MMP-9, and/or MMP-13 (particularly MMP-13) when treating cancer, inhibiting of metastasis, and inhibiting angiogenesis. It also is typically preferred to inhibit MMP-13 when treating osteoarthritis. See, e.g., Mitchell et al., J Clin. Invest., 97(3):761–768 (1996). See also, Reboul et al., J Clin. Invest., 97(9):2011–2019 (1996). Normally, however, it is preferred to use a drug that has little or no inhibitory effect on MMP-1 and MMP-14. This preference stems from the fact that both MMP-1 and MMP-14 are involved in several homeostatic processes, and inhibition of MMP-1 and/or MMP-14 consequently tends to interfere with such processes.
Many known MMP inhibitors exhibit the same or similar inhibitory effects against each of the MMPs. For example, batimastat (a peptidomimetic hydroxamic acid) has been reported to exhibit IC50 values of from about 1 to about 20 nM against each of MMP-1, MMP-2, MMP-3, MMP-7, and MMP-9. Marimastat (another peptidomimetic hydroxamic acid) has been reported to be another broad-spectrum MMP inhibitor with an enzyme inhibitory spectrum similar to batimastat, except that Marimastat reportedly exhibited an IC50 value against MMP-3 of 230 nM. See Rasmussen et al., Pharmacol. Ther., 75(1): 69–75 (1997).
Meta analysis of data from Phase I/II studies using Marimastat in patients with advanced, rapidly progressive, treatment-refractory solid tumor cancers (colorectal, pancreatic, ovarian, and prostate) indicated a dose-related reduction in the rise of cancer-specific antigens used as surrogate markers for biological activity. Although Marimastat exhibited some measure of efficacy via these markers, toxic side effects reportedly were observed. The most common drug-related toxicity of Marimastat in those clinical trials was musculoskeletal pain and stiffness, often commencing in the small joints in the hands, and then spreading to the arms and shoulder. A short dosing holiday of 1–3 weeks followed by dosage reduction reportedly permits treatment to continue. See Rasmussen et al., Pharmacol. Ther., 75(1): 69–75 (1997). It is thought that the lack of specificity of inhibitory effect among the MMPs may be the cause of that effect.
Another enzyme implicated in pathological conditions associated with excessive degradation of connective tissue is aggrecanase, particularly aggrecanase-1 (also known as ADAMTS-4). Specifically, articular cartilage contains large amounts of the proteoglycan aggrecan. Proteoglycan aggrecan provides mechanical properties that help articular cartilage in withstanding compressive deformation during joint articulation. The loss of aggrecan fragments and their release into synovial fluid caused by proteolytic cleavages is a central pathophysiological event in osteoarthritis and rheumatoid arthritis. It has been reported that two major cleavage sites exist in the proteolytically sensitive interglobular domains at the N-terminal region of the aggrecan core protein. One of those sites has been reported to be cleaved by several matrix metalloproteases. The other site, however, has been reported to be cleaved by aggrecanase-1. Thus, inhibiting excessive aggrecanase activity provides an additional and/or alternative treatment method for inflammatory conditions. See generally, Tang, B. L., “ADAMTS: A Novel Family of Extracellular Matrix Proteases,” Int'l Journal of Biochemistry & Cell Biology, 33, pp. 33–44 (2001). Such diseases reportedly include, for example, osteoarthritis, rheumatoid arthritis, joint injury, reactive arthritis, acute pyrophosphate arthritis, and psoriatic arthritis. See, e.g., European Patent Application Publ. No. EP 1 081 137 A1.
In addition to inflammatory conditions, there also is evidence that inhibiting aggrecanase may be used for treating cancer. For example, excessive levels of aggrecanase-1 reportedly have been observed with a ghoma cell line. It also has been postulated that the enzymatic nature of aggrecanase and its similarities with the MMPs would support tumor invasion, metastasis, and angiogenesis. See Tang, Int'l Journal of Biochemistry & Cell Biology, 33, pp. 33–44 (2001).
Various hydroxamic acid compounds have been reported to inhibit aggrecanase-1. Such compounds include, for example, those described in European Patent Application Publ. No. EP 1 081 137 A1. Such compounds also include, for example, those described in WIPO PCT Int'l Publ. No. WO 99/09000. Such compounds further include, for example, those described in WIPO PCT Int'l Publ. No. WO 00/59874.
In view of the importance of hydroxamic acid compounds in the treatment of several pathological conditions (particularly those associated with MMP and/or aggrecanase activity) and the lack of enzyme specificity exhibited by two of the more potent hydroxamic acid MMP-inhibitor drugs that have been in clinical trials, there continues to be a need for hydroxamic acids having greater enzyme specificity (particularly hydroxamic acids exhibiting little or no inhibitory activity toward MMP-1 and/or MMP-14). The following disclosure describes hydroxamic acid compounds that tend to exhibit such desirable activities.